The general aims are first, to determine something of the relation between a light stimulus incident on a humun eye and the visual signals generated by the rod and cone receptors which absorb the light; and second, to elucidate the neural mechanisms that modify these signals as they are transmitted through the retina. Proposed areas for investigation include cone sensitization by lateral interaction in light and dark adaptation; the retinal distribution of blue-sensitive cones; and the properties of vision mediated by light adapted rods.